This calculation is commonly used to measure income disparity and is formally known as the income quintile share ratio (S80/S20). It represents the average (mean) income of the highest-earning 20 percent of households divided by the average income of the lowest-earning 20 percent. The Federal Reserve Bank of St. Louis describes this measure as “the ratio of average (mean) income for the highest earners (top 20%) divided by the average income of the lowest earners (bottom 20%)” (FRED Blog, Measuring income inequality as a ratio, May 26 2022. Federal Reserve Bank of St. Louis).